Chlorine bleaching compositions having hypochlorite as bleaching agent generally provide bleaching performance which is superior to oxygen-based compositions, such as those where the bleaching agent is perborate, percarbonate or peracid (e.g. diperazelaic, diperisophthalic and the like). Chlorine based bleaching compositions are known in both liquid and dry forms.
Among dry chlorine or bromine based compositions are those where halide ions (i.e. chloride or bromide) are oxidized by peroxymonosulfate to form hypochlorite or hypobromite following dissolution in aqueous solution. Thus, for example, U.S. Pat. No. 4,028,263, inventor Gray, issued June 7, 1977, discloses use of a peroxymonosulfate and a bromide source for hypobromite bleaching, and U.S. Pat. No. 4,116,878, inventor Deutscher et al., issued September, 1978, discloses a composition which generates hypobromite and includes amides, such as urea, to reduce dye damage.
Bromide is oxidized to form hypobromite at a considerably faster rate than chloride under similar conditions. Indeed, the oxidation of chloride by peroxymonosulfate under typical wash conditions is very slow, and the amounts of materials necessary to generate effective concentrations of hypochlorite for bleaching are not practical. Thus, activators have been sought for peroxymonosulfate bleaching systems, particularly for those generating hypochlorite.
In a technical service report dated Feb. 1, 1970 by American Potash & Chemical Corporation, it was reported that certain ketones (i.e. acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone), activate monopersulfate bleach in the presence of an alkaline buffer providing a pH of at least 8. U.S. Pat. No. 3,822,114, inventor Montgomery, issued July 2, 1974 discloses peroxygen bleaching compositions which include a peroxygen bleaching compound, such as water-soluble monopersulfates and monoperphosphates, and an aldehyde or ketone activator compound for the peroxygen compound. The certain aldehydes or ketones disclosed are said to activate the peroxygen compounds in aqueous solution having a pH of about 7 to about 12, and a preferred embodiment includes the optional addition of a water-soluble chloride salt to yield bleaching of a hypochlorite type.
Because both chlorine and oxygen based bleaching systems tend to be incompatible with various other desirable laundry additives, such as enzymes and optical brighteners, attempts have been made to delay the formation of bleaching agent.
U.S. Pat. No. 4,421,664, inventors Anderson et al., issued Dec. 20, 1983 discloses an encapsulated oxidant bleach composition combined with a reducing agent which reduces the oxidant composition when released from the encapsulating coating and provides a delay in the concentration of oxidant bleach to permit functioning of an enzyme in the composition. The reducing agents include salts of sulfur oxyacids such as ammonium sulfite, sodium sulfite, sodium thiosulfite, sodium metabisulfite, potassium metabisulfite, and lithium hydrosulfite. The oxidant compounds include those capable of having chlorine liberated in the form of free chlorine or hypochlorite, such as alkali metal dichloroisocyanurate. Peroxy bleach compounds are also disclosed, including the alkaline metal salts of perborates, percarbonates, persilicates, persulfates, and perphosphates.
Thus, on one hand inorganic peroxygen bleaching compositions desirably include activators, particularly for monopersulfate and monoperphosphate systems generating hypochlorite, in order to provide effective concentrations of the bleaching agent under typical wash conditions; but, on the other hand it has been difficult to protect various desirable laundry additives from attack when effective bleaching concentrations of peroxygen bleaching agents are present.